Field of the Invention
The present invention relates to irrigation nozzles or sprinkler heads, as used in automatic lawn sprinkling and other irrigation systems.
Discussion of Related Art
In-ground irrigation nozzles (e.g., sprinkler heads) have been on the market for many years and come in many different configurations for depositing a selected amount of irrigation fluid (e.g., water) upon a designated landscape area through a spray. For a good performing spray, the amount of water sprayed is minimized to: (a) reduce runoff, yet (b) still adequately irrigate the entire area and (c) do so in a reasonable amount of time. The amount of water used is defined as “precipitation rate” (or “PR”) commonly measured and expressed in “inches per hour” or “in/hr.”
Uniform distribution is desirable and the uniformity in distribution of that water is commonly measured and expressed in terms of the Scheduling Coefficient (“SC”), which can be used as a multiplier to determine how much longer a spray must run in order to irrigate the driest patch to the same amount as the mean application rate for the entire area. Optimum precipitation rates depend on soil conditions, but in general it is desirable to have an irrigation nozzle assembly (or sprinkler) with a PR of 1 in/hr or less. SC values of 1.5 or less are considered good within the irrigation industry, with an absolute best being 1.0.
In order to achieve good spray performance, some nozzles on the market today utilize rotating parts, friction plates, and viscous brakes. U.S. Pat. No. 6,942,164, to Walker is a useful example of a rotating sprinkler or nozzle. While these rotator nozzles can achieve a PR around 0.5 in/hr and good distribution, they are relatively costly compared to fixed sprays. Current sprinkler heads with fixed sprays have no moving parts and are used in short to medium spray throw distances (up to 15 feet or so), but have PR's greater than 1 in/hr and varying spray distribution, including dual spray designs.
Current fixed sprays are “non-fluidic” and so rely on spreading an impinging jet into a fan spray (i.e., a liquid sheet). This shears the spray and so can make finer drops having lower velocity. As a result, these nozzles have high PR (about 1.4 and above), especially at longer throws (throw is also referred to as radius, in some applications). For a 360 deg spray (i.e., a full spray), non fluidic nozzles typically use a swirl spray that produces a conical sheet. Swirling sheets also produce fine drops and low velocity, resulting in a low throw (or short radius).
Fixed sprays are available in throws (or radii) ranging from 5′ to 15′ with a 25% throw adjustment for each nozzle. Achieving throws from 5′ to 10′ at low PR (PR≤1) is relatively easy even for non fluidic sprays. However as the throw increases (i.e. for 12′ and 15′), velocity and droplet size become critical, and PR increases (PR>1.4) for non-fluidic sprays.
Applicants have discovered that fluidic spray nozzles may be designed for a wide range of PR values, and particularly PR≤1 all through the range of 5′-15′, but these results required a significant amount of new development work, experimentation and testing.
Generally speaking, fluidic oscillators are known in the prior art for their ability to provide a wide range of liquid spray patterns by cyclically deflecting a liquid jet. Examples of fluidic oscillators may be found in many patents, including U.S. Pat. No. 3,185,166 (Horton & Bowles), U.S. Pat. No. 3,563,462 (Bauer), U.S. Pat. No. 4,052,002 (Stouffer & Bray), U.S. Pat. No. 4,151,955 (Stouffer), U.S. Pat. No. 4,157,161 (Bauer), U.S. Pat. No. 4,231,519 (Stouffer), which was reissued as RE 33,158, U.S. Pat. No. 4,508,267 (Stouffer), U.S. Pat. No. 5,035,361 (Stouffer), U.S. Pat. No. 5,213,269 (Srinath), U.S. Pat. No. 5,971,301 (Stouffer), U.S. Pat. No. 6,186,409 (Srinath) and U.S. Pat. No. 6,253,782 (Raghu), which are summarized below.
The operation of most fluidic oscillators is usually characterized by the cyclic deflection of a fluid jet without the use of mechanical moving parts. Consequently, an advantage of fluidic oscillators is that they are not subject to the wear and tear which adversely affects the reliability and operation of pneumatic oscillators and reciprocating nozzles. The fluidic oscillators described in U.S. Pat. No. 3,185,166 (Horton & Bowles) are characterized by the use of boundary layer attachment (i.e., the “Coanda effect,” so named for Henri Coanda, the first to explain the tendency for a jet issuing from an orifice to deflect from its normal path (so as to attach to a nearby sidewall) and the use of downstream feedback passages which serve to cause the jet issuing from a power nozzle to oscillate between right and left side exit ports.
At the risk of boring those having skill in this rather specialized art, a rather substantive background is provided here. It is understood that the three-dimensional character of the flow from such fluidics can take a variety of forms depending upon the three-dimensional shape of the fluidic. For example, oscillators described in U.S. Pat. No. 4,052,002 (Stouffer & Bray) are characterized by the selection of the dimensions of the fluidic such that no ambient fluid or primary jet fluid is ingested back into the fluidic's interaction region, which yields a relatively uniform spray pattern made up of droplets of more uniform size. The absence of inflow or ingestion from outlet region is achieved by creating a static pressure at the upstream end of interaction region which is higher than the static pressure in outlet region. This pressure difference is created by a combination of factors, including: (a) the width T of the exhaust throat is only slightly wider than power nozzle so that the egressing power jet fully seals the interaction region from outlet region; and (b) the length D of the interaction region from the power nozzle to throat, which length is significantly shorter than in prior ‘fluid ingesting’ oscillators. It should be noted that the width X of control passages is smaller than the power nozzle. If the width of power nozzle at its narrowest point is W, then the following relationships were found to be suitable, although not necessarily exclusive, for operation in the manner described: T=1.1-2.5 W and D=4-9 W, with the ratios of these dimensions also being found to control the fan angle over which the fluid is sprayed. By adding a divider in this fluidic's outlet region, it becomes what can be referred to as two-outlet oscillator of the type that might be used in a windshield washer system. See, for example, U.S. Pat. No. 4,157,161 to Bauer.
The fluidic oscillators described in U.S. Pat. No. 4,231,519 (Stouffer, reissued as U.S. Pat. No. RE 33,158), are also unique in that they employ yet another fluid flow phenomena to yield an oscillating fluid output. The oscillators of U.S. Pat. No. 4,231,519 are characterized by their utilization of the phenomena of vortex generation, within an expansion chamber prior to the fluidic's throat, as a means for dispersing fluid. It comprises a jet inlet that empties into an expansion chamber which has an outlet throat at its downstream end. It also has an interconnection passage that allows fluid to flow from one side to the other of the areas surrounding the jet's inlet into its expansion chamber. The general nature of the flow in such fluidics is that vortices are seen to be formed near the throat. As the vortices grow in size they cause the centerline of the fluid flowing through the expansion chamber to be deflected to one side or the other such that the fan angle of the jet issuing from the throat ranges from approximately +45 degrees to −45 degrees. The result of these flow oscillations is a complicated spray pattern, which at a given instant takes a sinusoidal form (similar to that shown in FIG. 6(e) in commonly owned U.S. Pat. No. 6,805,164).
The fluidic oscillators disclosed in U.S. Pat. No. 5,213,269 (Srinath) and U.S. Pat. No. 5,971,301 (Stouffer) are referred to as “box oscillators” having interconnects which serve to help control the oscillating dynamics of the flow that exits from the fluidic's throat. For example, the effect of these interconnects, assuming that they are appropriately dimensioned relative to the other geometry of the fluidic, is generally seen to be about a doubling of the fan angle of the fluid exiting from the fluidic's throat. FIG. 8(a) from U.S. Pat. No. 5,213,269 shows an embodiment in which the interconnect takes the form of passage that connects points on opposite side of the fluid's throat. FIG. 8(b) from U.S. Pat. No. 5,971,301 shows an embodiment in which the interconnect takes the form of a slot in the bottom wall of the fluidic's interaction region.
U.S. Pat. No. 6,253,782 (Raghu) discloses a fluidic oscillator of the type that provides a shaped interaction region having two entering power nozzles and a single throat through which the resulting fluid flow exits the fluidic oscillator. See FIGS. 9(a)-(b). The jets from the power nozzles are situated so that they interact to form various vortices which continually change their positions and strengths so as to produce a sweeping action of the fluid jet that exits the throat of the fluidic. In a preferred embodiment, the interaction region has a mushroom or dome-shaped outer wall in which are situated the power nozzles. U.S. Pat. No. 6,186,409 (Srinath) discloses a fluidic oscillator which has two power jets entering a fluid interaction region from the opposite sides of its longitudinal centerline. The jets are fed from the same fluid source, and are unique because they employ a filter between the jet source and the upstream power nozzles to remove any possible contaminants in the fluid.
In order to function properly, fluidic oscillators need to have proper sealing so as to not cause leaking across flow channels. The typical construction for the fluidic oscillator has been to fabricate the fluidic circuit in one surface and sealed with another surface. FIG. 1 depicts a crossover-type fluidic element 10 formed in a body member 11. Recesses 13 are typically formed in surface 12 by injection-molding, and a cover plate 16 is placed against a surface to seal the fluidic element. In U.S. Pat. No. 4,185,777, the fluidic circuit element 20 is injection-molded in a chip member 21 (or “chip”) which is then sealed by abutting the surface against another member, and in order to prevent leakage, the molded element is force-fitted into a housing 22. (See FIG. 2 in the '244 patent.) In U.S. Pat. No. 6,948,244, a method for molding fluidic circuit “chips” is described. This detailed background is provided, in part, to illustrate the concepts and nomenclature of fluidic circuits, an area of particular expertise for this applicant, and the above identified references are incorporated by reference.
Irrigation nozzles such as lawn sprinklers, generally, and fluidic oscillators, generally, are distinct technologies and each are known to persons in their respective areas of the different arts, but there has not yet been a satisfactory way to combine them into a reliable and cost effective structure or method for generating adequately high velocity and large droplet size in a manner that would be advantageous for irrigation applications, where a long throw is desired with low flow rate, so that the “precipitation rate” can be reduced.
Fluidic sprays rely on a jet that oscillates to produce a fan spray. Thus, the output is not a liquid sheet but a stream that has high velocity with good droplet size. This knowledge has been applied to the long felt need to provide a reliable, inexpensive and uniform system and method for irrigating a selected region.
Other considerations have also been addressed. Sprinkler systems used for irrigating lawns and parks must be serviced periodically, to prevent damage from expansion of freezing water in the pipes and sprinkler heads. Annually, the systems are cleared of water, often with compressed air, to drive all water out of the pipes and sprinkler components. The following spring, water is re-introduced into the system and that water must first displace the air in the pipes.
Recent advances in fluidics technology have been evaluated for use in irrigation systems, partly because fluidic oscillators can be adapted to provide a very uniform pattern of fluid dispersion over an area selected for irrigation. These new fluidic circuits provide significantly different hydraulic impedance to the flow of water, when compared to an open spray nozzle, however, and so the introduction of water into a system having trapped air in the lines presents a new challenge.
Specifically, the applicants have discovered a problem with a fluidic equipped prototype sprinkler or nozzle assembly. The issue was that under some conditions, mainly after winterization of a residential or commercial irrigation system, there is an air void in the plumbing leading up to the fluidic equipped nozzle. When the water is turned back on to the system a wave of water travels at a high rate of speed down the plumbing, displacing the air. This instantaneous impact created by the density difference between the remaining air void and wave of water generates excessive loads that can damage a fluidic nozzle insert or force it out of the housing. The impact force produced by the “surge” turns out to be quite high, close to 30 lbf.
There is a need, therefore, for a convenient, reliable and inexpensive assembly structure and method for protecting a fluidic equipped irrigation nozzle from the water-hammer like effect of this first inrush of water.